Nepenthes mollis Danser (1928: 338

Robinson, Alastair S., Golos, Michal R., Barer, Marc, Sano, Yosuke, Forgie, Jennifer J., Garrido, Diego, Gorman, Chandler N., Luick, Adi O., Mcintosh, Nick W. R., Mcpherson, Stewart R., Palena, Gregory J., Pančo, Ivan, Quinn, Brian D. & Shea, Jeff, 2019, Revisions in Nepenthes following explorations of the Kemul Massif and the surrounding region in north-central Kalimantan, Borneo, Phytotaxa 392 (2), pp. 97-126 : 119-123

4. Nepenthes mollis Danser (1928: 338 , fig. 14) descr. emend. A.S.Rob. & Golos ( Figs. 11−12 )

Type: — Borneo, Kalimantan, W. Koetai, G. Kemoel, ± 1800 m, 17 October 1925, Endert 4282 (holotype BO!) [pitcherless climbing stem with male inflorescence; single sheet labelled “Unicum!”] .

= Nepenthes hurrelliana Cheek & A.L.Lamb in Cheek et al. (2003: 118, figs. 1–3), syn. nov.

Type: —Borneo, Sabah, Gunung Lumarku, August 1999, Lamb & Surat 145/99 (holotype SAN, iso- K).

− Nepenthes fusca × N. veitchii in Phillipps & Lamb (1988: 26, 1 fig.).

− Nepenthes sp. in Phillipps & Lamb (1996: 150, fig. 80) and Salmon (1999: 24, fig. 1).

− Nepenthes sp. B in Clarke (1997: 142, fig. 98) and Steiner (2002: 110, figs. 172–173).

Description 3: —Epiphytic or terrestrial climbing or pendent shrub, to 5(–10) m tall. Stems of rosettes terete, 7–10 mm in diameter, internodes 0.6–2.5 cm long; vining stems ±terete, 5–9 mm in diameter, internodes 9–15 cm long, axillary buds nodular, ca. 5–7 mm in diameter, 1–3 mm tall, 5–12 mm above the axil, occasionally apically filiform to 5 mm. Leaves of rosettes coriaceous, petiolate, lamina obovate, becoming narrowly obovate to oblanceolate with increasing internode length, 10–15 cm long, 3.5–5 cm wide, apex retuse, becoming acute, not peltate, base gradually attenuate, petiole canaliculate, 2–3.5 cm long, not winged, not decurrent, sheathing and clasping the stem for its entire circumference. Longitudinal veins (1–)2–3 on either side of midrib, restricted to outer third of lamina where they run parallel to the laminar margin, inconspicuous. Pinnate veins numerous, irregularly reticulate, indistinct. Tendrils ca. 1.5 times longer than the laminae, without curl. Leaves of tall stems coriaceous, initially petiolate and winged, to 5 cm long with wings 0.3–0.8 cm wide, sheathing stem for 3/5–4/5 its circumference, becoming sub-petiolate and shortly decurrent to ca. 2 cm, thereafter sessile and strongly decurrent with ±parallel margins towards the base, lamina oblanceolate to oblong-spathulate, (11.5–)14–20(–24) cm long, 3.5–5(–6.5) cm wide, apex acute, rarely sub-peltate, to obtuse, base almost wholly amplexicaul, strongly oblique and decurrent into two wings for 2–5(–6) cm, usually 1/4–1/3 of total internode length, wings ca. 0.8–1.4 cm wide either side of stem, thereafter gradually attenuate into stem, longitudinal veins 2(–3), inconspicuous in living material. Tendrils ca. 2 times longer than the laminae, typically with 2.5 curls. Lower pitchers sub-cylindric, 9–15(–21) cm tall, 2–5.5 cm wide, with fringed wings 2–5 mm wide throughout, fringe elements 3–7 mm long, 3–5 mm apart; peristome horizontal between wings, thereafter strongly oblique, becoming vertical in the rear half and slightly recurved over pitcher opening towards lid, sub-cylindric at the front, 3–7 mm wide, rear part flattened, ca. 5 times wider than at front, usually without marginal lobes, ribs pronounced ca. 0.8 mm apart, teeth ca. 0.8–1 mm long. Lid ovate, complanate, base cordate, apex obtuse to retuse, 2.5–5 cm long, 1.5–3 cm wide, with pronounced abaxial midline rib and a prominent keel, projecting 4–7 mm below lid and hooked towards rear, keel minutely and densely glandular, glands crateriform, ca. 0.2 mm in diameter, and pubescent, apical protuberance absent. Spur simple, filiform, 0.6–1.1 cm long. Intermediate pitchers sub-cylindric to slightly infundibuliform, gradually widening from base to apex, 12–22(–30) cm long, 3.2–8 cm wide, with fringed wings in the upper half, (0–)1–2(–5) mm wide, fringed elements 2–3(–7) mm long, 2–4 mm apart, or with wings occasionally reduced to prominent ridges; peristome broad, often slightly raised between wings, front 1/2 to 2/3 near horizontal, abruptly becoming vertical in the rear 1/2 to 1/3, forming a column 4–8(–12) cm tall, 3–15 mm wide at the front of the pitcher, sub-cylindric, the raised, rear part flattened, up to 5 times wider than front of pitcher, outer edge sinuate, shallowly 1–3–lobed, ribs strongly pronounced, 1–1.5(–2) mm apart, 0.3–1 mm high, teeth 1–1.5 mm long at the front of the pitcher, 2–3.5 mm long on the column, where they project downwards at an acute angle into the mouth. Lid triangular-ovate with a slightly cordate base, 2.5–8 cm long, 2–4 cm wide, apex rounded, lower surface with pronounced basal keel projecting 8–10 mm below lid on a base about as long, strongly hooked towards rear, nectar

3 This emended description incorporates details from the description of Nepenthes hurrelliana in Cheek et al. (2003), observations of same in situ on Mt. Murud, the type description of N. mollis ( Danser 1928) , and measurements made of N. mollis in situ in the Kemul Massif.

glands extremely dense on basal appendage and immediately adjoining part of lid, orbicular, 0.15 mm in diameter with a thin, raised border, keel often slightly pubescent, abaxial surface of lid with thinly scattered smaller glands mainly in the basal half, orbicular to shortly transversely elliptic, 0.15–0.25 mm long, often fewer or absent from apical half, apical protuberance sometimes absent, otherwise umbonate-conic to filiform, to ca. 5 mm long, 1 mm in diameter. Spur simple, filiform, 1–1.5 cm long, slightly recurved. Upper pitchers infundibular throughout, 18–24 cm long, 6–9 cm wide just below the mouth, often abruptly constricted at peristome, wings reduced to prominent ridges; form of peristome similar to intermediate pitchers, but 4–6 mm wide at front of mouth, rear, flattened part only up to 3.5 times wider than front of pitcher and usually slightly more cylindric, column 5.5–9 cm tall. Lid triangular-ovate with a cordate base, 3.5–5 cm long, 2–3 cm wide, midline rib prominent with large, pubescent glandular keel and usually with a 2–3 mm apical appendage with large pitted glands. Spur filiform, up to 25 mm long. Male inflorescence 20–27 cm long, 80–150 flowers, peduncle 6–9(–12) cm long, 3–4 mm in diameter at the base, rachis 10–15 cm long, partial-peduncles 2-flowered, bifurcating 1–1.5 mm from the base, base with bract, linear, rarely bifurcated, patent to ascending, 3–4 mm long, caducous, pedicels 7–10 mm long, tepals deep burgundy to green, elliptic, 3.5–4 mm long, 2–3 mm wide, deflexed and somewhat concave, adaxial surface with 30–40 deeply pitted glands, apex rounded to acute; staminal column 2.8–3.5 mm long, anther head 1.5 mm in diameter, thecae and pollen grains yellow. Female inflorescence 22–30 cm long, 40–70 flowers, peduncle 12–15 cm long, rachis 10–12 cm long, partial-peduncles 2- flowered, 5–7 mm long, without bracts, pedicels 5–10 mm long, tepals elliptic, apex acute, 4–5(–6) mm long, ovary sessile, ellipsoid, 5 mm long. Seed 10–12 mm long. Indumentum abundant, consisting of coarse, brown to rufous hairs, partly shorter, branched and spreading, partly simple and up to 1.2–1.8 mm long, especially dense on young foliage, the stem, leaf margins, the abaxial leaf surface, the abaxial midrib, basal adaxial midrib and on the tendril, as well as more sparsely on the exterior surface of the pitchers, including the adaxial surface of the lid, and the abaxial surface mainly on the basal keel. The indumentum of the adaxial leaf surface differs in being covered with short, simple, whitish hairs. The inflorescences are densely pubescent with woolly, rufous hairs in the main axis, while the partial-peduncles, pedicels, abaxial tepal surface, tepal margins and staminal column are covered with shorter, simple hairs. Colour of mature stems usually green to olive green, lower pitchers often olive green to yellowish green, sometimes blotched with deep red or purple, peristome purple to brown and striped with yellow or green, upper pitchers entirely yellowish green to green blotched with red or suffused with deep red throughout.

Phenology: —Flowering was observed in Kemul Massif plants in early July. Flowering has been observed on Mt. Murud ( Sarawak) in July and October (AR pers. observ.).

Distribution and ecology: —Outside of north-central Kalimantan (Kemul Massif), Nepenthes mollis has been recorded (and ascribed to N. hurrelliana ) from Brunei (Bukit Pagon), southwestern Sabah (Mt. Lumarku, Meligan Range), and northeastern Sarawak (Mt. Mulu, Mt. Murud) ( Cheek et al. 2003, Phillipps et al. 2008). However, the plants from Mt. Mulu are atypical in a number of respects (AR, BQ pers. observ., Phillipps et al. 2008); coupled with the established presence of N. sp. Bagong on Mt. Mulu, it cannot be unequivocally stated here whether the plants in the cited literature describe one taxon or the other without pointed investigation.

The known elevational range is that previously reported for N. hurrelliana : 1300–2400 m ( Phillipps et al. 2008). On Mt. Murud and the Kemul Massif, plants occur in high montane forest, persisting in relative shade but growing most strongly in canopy breaks and more open areas. On Mt. Murud, where the expansive sandstone escarpment that makes up the mountain emerges above 2100 m, plants also occur in exposed sites, occupying humus pockets within a rocky, elfin forest habitat where its congeners N. lowii and N. murudensis Culham ex Jebb & Cheek (1997: 66) predominate.

Nepenthes mollis has been documented (as N. hurrelliana ) to form natural hybrids with N. chaniana and N. lowii on Batu Buli ( Phillipps et al. 2008, Scharmann 2010a, Scharmann 2010b) and also with N. veitchii ( McPherson 2009) .

Conservation status: —Though Nepenthes mollis is known from a relatively small number of mountains, these span a wide area in north-central Borneo. Its range is therefore large and encompasses dozens of peaks of suitable elevation that have not been explored or at least well botanised, making a wider distribution likely. Large populations are afforded protection in Pulong Tau NP ( Sarawak), with additional populations protected in Ulu Temburong NP ( Brunei). The remaining sites occur at high elevations on steep terrain unlikely to be subject to logging. The species therefore qualifies as Least Concern when evaluated against the IUCN 3.1 criteria ( IUCN 2012).

Notes: — Salmon (1999) recognised that the taxon that would be described as N. hurrelliana ( Cheek et al. 2003) matched the type material of N. mollis closely, noting two exceptions: that the leaf bases of the N. mollis type are decurrent for 4–6 cm, while those of N. hurrelliana are decurrent for 1–2 cm; and that the pedicels of N. mollis (a male inflorescence) lack bracts, while those of N. hurrelliana bear 3–4 mm long bracts at the base of the pedicels.

In addressing these inconsistencies, it is first necessary to better characterise Nepenthes hurrelliana . When the species was described, it was relatively poorly known, the protologue ( Cheek et al. 2003) notably describing the “Rosette and short stems [as] unknown”. Since then, numerous excursions have been made to Mt. Murud to study N. hurrelliana in situ (for example, 6 separate ascents of Murud have been made between AR and SM alone). Observations have found that the leaves of plants in the rosette stage are strongly petiolate, lack wings and exhibit no apparent decurrency; with increasing internode length, however, there is a shift towards the production of oblanceolate leaves with winged petioles that are slightly decurrent, while in tall climbing stems the leaves become sub-petiolate to wholly spathulate-lanceolate and decurrent for ca. 3–5 cm, that is, decurrent for approximately 1/3 of any given climbing internode. This same progression was noted in N. mollis in the Kemul Massif and is documented in Fig. 12 . This trait, which is uncommon in Nepenthes , presents a particular problem of material consistency in terms of the specimens collected for common reference, whereby the vertical position along the stem of the collected material affects not only pitcher morphology but also the morphology of the leaf bases! Explorations of Mt. Murud have shown that there is considerable variation in leaf decurrency according to the length of the stem, but moreover that there is overlap in the degree of decurrency between N. hurrelliana in situ, the type material of N. mollis , and living specimens of N. mollis observed in the Kemul Massif.

With regard to the floral inconsistencies, while measuring living male inflorescences of N. mollis in situ, it was noted that bracts were present on the pedicels of many of the flowers, but not on all. Additionally, examination of dead male inflorescences on the same plants found scant evidence of floral bracts. This suggests either that bracts are produced inconsistently or, more likely, that the bracts might be caducous, which could explain the stated absence of bracts from the type material. Surprisingly, examination of the N. mollis type material (Endert 4282) held at BO found what appear to be several bracts towards the distal part of the damaged inflorescence, which suggests that these might have been overlooked by Danser. Field observations show that bracts do appear to be more consistently produced in the Mt. Murud population, but inconsistency in bract production has been noted between wild populations of other species of Nepenthes , most notably N. robcantleyi Cheek (2011: 678) and Nepenthes graciliflora Elmer (1912: 1494) (AR pers. observ.). The presence of floral bracts is therefore perhaps best regarded as a secondary diagnostic in Nepenthes except where extensive field observations support the inferences made from pressed materials.

The Nepenthes mollis on Mt. Murud represent the most visited and most extensive populations of this species currently known, and occur along much of the> 6.5 km (2000–2400 m elevation) ridge used as the main approach to the mountain summit, also a site of biannual religious pilgrimage. The greatest range of diversity in form and colour is recorded here, no doubt partly because of the number of visits made to the habitat, but also because the plants occur in a range of situations from dense forest to exposed expanses of rock. This diversity is especially apparent in the neck of the peristome, which in some plants can become extremely exaggerated, more so than at other known sites. Whether or not the species evolved here is a matter of conjecture, but the mountain is certainly one of its major strongholds.

Additional specimens examined:— BRUNEI: Cantley s.n. (K! [3 sheets]), Gunong Pagon Priok, 5700 ft [= 1737 m], 20 October 1984 [separate lower pitchers; lower pitcher with leaf, rosette with lower pitcher; lower pitcher with leaf fragment]. SABAH: Hurrell s.n. (K!), S. Sabah, Gunung Luma[r]ku, 1700 m, 8 June 1995 [stem with intermediate pitcher; annotated Nepenthes “hurrellii”; labelled as paratype of N. hurrelliana but not cited in protologue].

Notes on specimens examined: —The isotype of N. hurrelliana at K was not located by MG during a visit in July 2018 and may have been misplaced.

Figures

FIGURE 11. Nepenthes mollis Danser. A—rosette with right lower and left intermediate pitchers. B—climbing stem bearing upper pitchers and male inflorescence, note increasing leaf decurrency. C—adaxial detail of a climbing stem leaf showing leaf attachment. D—detail of leaf margin and adaxial surface. E—detail of upper pitcher lid, left adaxial surface, middle abaxial surface, right lateral view showing keel. F—cross section of peristome. G—male flowers. H—dehiscing seed capsules. Scale bars: A, B, C, E, F = 1 cm, D, H = 5 mm, G = 2 mm. Based on Endert 4282 and supplemented with photographs and measurements made of in situ material. Illustrated by M. Barer.

FIGURE 12. Pitchers and leaves of Nepenthes mollis. Top row Kemul Massif, middle row Mt. Murud. A & D—lower pitchers. B & E—intermediate pitchers. C & F—upper pitchers. G—petiolate bases of rosette leaves (Kemul Massif). H—decurrent bases of climbing stem leaves, abaxial perspective, and I—lateral perspective (both Kemul Massif). Photographs A, B, D, E, F, H by A.S. Robinson; C, I by M.R. Golos; G by S.R. McPherson.